During client synchronization, using ValidateSceneBeforeLoading to ignore already loaded scenes fails

[NoelStephensUnity]

Description

When a user implements ValidateSceneBeforeLoading to bypass loading certain scenes (security or platform specific purposes) and ValidateSceneBeforeLoading is invoked during a client's synchronization stage then the entire remaining portion of the synchronization process is completely halted.

Reproduce Steps

1. Create a project where clients invoke ValidateSceneBeforeLoading
2. Create a neutral scene that has no impact on whether the client loads it or not
3. Have the client-side return false when the neutral scene is attempting to load
4. Start the host and connect a client

Actual Outcome

The client never finishes the synchronization process and never fully connects to the server.

Expected Outcome

Users should be able to use ValidateSceneBeforeLoading during the synchronization process without it impacting the synchronization process.

Environment

• OS: Windows 10 (will happen on all platforms)
• Unity Version: 2021.2.10f1
• Netcode Version: 1.0.0-pre.7

[NoelStephensUnity]

This is fixed in #1883.